This invention relates to ball screw and nut assemblies, and more particularly to the manner of routing the train of balls which exit one end of the nut and move around to the other end of the nut in a continuous circuit.
Ball return systems for ball nuts have, in the past, often utilized radially extending openings at each end of the nut which communicate with the internal ball raceway to connect an external ball return tube which provides the return path. To avoid this external structure where it is not feasible to use it, other prior art ball nuts have utilized longitudinal return passages extending internally in an axially parallel direction through the nut body into which the balls are fed at one end and returned at the other to the helical ball path. Typically, end closures or caps for such nuts have been provided to turn the ball circuit reversely, with the end closure caps being grooved to provide channels forming part of the ball return circuit.
In some such prior art systems, the end closures have been molded from a plastic material and fasteners have been employed to secure them to the end walls of the nut. Plastic end closures are disclosed in prior U.S. Pat. Nos. 4,074,585 and 4,677,869. In these systems, the nut and screw were machined of the typical steel material used by ball nut and screw manufacturers to enable the mechanisms to bear heavy loads with maximum wear resistance. Because the trackway for the train of balls is formed in steel bodies, high mechanical efficiencies can be obtained with low torque inputs and ball nut and screw assemblies of this type are particularly suited for use where precision must be maintained.